Fundamental beam studies of radical enhanced atomic layer deposition of TiN

TiN films were deposited using radical enhanced atomic layer deposition (REALD) in an ultrahigh vacuum beam system. The REALD cycle used for the film deposition consisted of separate, sequential exposures of $TiCl4,$ deuterium atoms, and nitrogen atoms. By using this three step deposition process with independently controlled beams of $TiCl4$ molecules, deuterium radicals, and nitrogen radicals, it was possible to monitor each step in the REALD cycle, measuring the sticking and reaction probabilities of each of these species on silicon as a function of surface temperature using a quartz crystal microbalance. Results from the ex situ XPS analysis of the deposited films are promising and suggest that deuterium radicals can abstract Cl from $TiClx$ surface species for substrate temperatures as low as 300 K. The films display low residual chlorine content $(<0.3%)$ when the D atom exposure is sufficiently large. The results from the third stage in the REALD TiN process are consistent with the addition of approximately stoichiometric amounts of nitrogen. However, the data suggest that during the first few REALD cycles, the nitrogen diffuses into and reacts with the underlying silicon substrate.